Looks good!

Belt Drive
 

https://cimg0.ibsrv.net/gimg/bikefor...5922d86b1f.jpg
https://cimg1.ibsrv.net/gimg/bikefor...de6e032e68.jpg
Finally got round to converting my MK1 to belt drive with a mixture of AliExpress purchases and Brompton spares.

I'd be concerned about that tensioner coming apart. It's only plastic and you've removed a good chunk.

Also,Kinetics says it's ok to run those belts through tensioners,but Gates says no.
https://www.gatescarbondrive.com/res...g-and-tension#

I agree with you, even if it works, such a tensionner cannot provide the tension rated by Gates and will probably reduce the belt and sprocket life.

Time will tell on the belt, but I've done 500 miles with the tensioner as is (I had a chain on it previously) and it's fine - there's actually a fair bit of material on the other side of the derailleur hanger.

The tensioner is only there to help with the fold - the belt is kept on the rear sprocket by the snubber wheel you can see in the second pic. It's the same method Ben from Kinetics uses on his Brompton conversions and seems to work fine

Yes, I know what Ben Cooper of Kinetics does.

But I doubt that it provides the belt tension specified by Gates?

If not, it can "work" = no tooth jump, but the belt and sprocket might wear faster.

I'd be interested in seeing it folded. I've seen Brommies with the belts and it's seriously twisted backwards when folded.

The tension is provided by your legs! Using overall tension to manage tooth jump is only necessary when there's no snubber wheel in play.

You should read the specifications of Gates!

Now, you can of course do what you think is good if you think that you know better the requirements of a Gates Carbon Drive belt than Gates.

From your link: "Proper belt tension is essential for optimum operation of the Gates Carbon Drive System. Lack of belt tension can lead to tooth jump or “skipping,” when the teeth of the belt slide over the teeth of the rear sprocket. Too much tension can damage the bearings within the rear hub, can cause the system to drag, and can increase the wear of your drive system."

I think we can agree that there's no danger of too much tension in my setup. And the snubber wheel prevents tooth skipping. So where's the problem?

Bear in mind that when you set the tension in a 'normal' Gates set up, you're only tensioning the belt at rest. You'll exert forces far, far in excess of those stated on the upper part of the belt under load.

You can ask Gates.

But with the tension recommended by Gates, the tension exists on the upper and lower sides of the belt, not only on the upper one.

I don't need to ask Gates - their document you linked to made it clear that tension is only required to prevent tooth skipping, a job the snubber wheel handles in this application.

Not when you're pedalling under load - the tension will be mostly on the upper side with very little (if any) on the lower side.

Oh dear!

https://cimg1.ibsrv.net/gimg/bikefor...92a4443b1f.jpg

How remove Birdy Gen 2 crankset?
 

Hi, trying to swap the original crankset off my old Birdy Gen 2 but can’t figure out how to get them off, and nor can my local bike shop. I’ve bought 3 different cran pullers and none work - the standard one way too small, 23.35mm slightly too small and 25mm seems right size but cannot get it to screw in. Any ideas please? Or any hacks to remove them without a crank puller? They’re being replaced so don’t mind if they get damaged getting them off (as long as rest of bike unharmed!). Thanks!🙏

You loosen the holding bolt of the crank you want first and ride slowly around the vicinity. The moment you sense the crank loosening, you tighten the holding bolt, but not fully, and loosen the bolt for the other crank and repeat. All this needs to be done carefully to prevent damage to the cranks.

Brilliant, I’ll give that a try thank you

I’ve not got the cranks off yet but when I do would like to replace the BB - does anyone know the spec for the BB for a Birdy Gen 2 please?

bsa 68mm , and the diameter of the axe you should to measure your self or check the model and brand to the crank set

I bought a Birdy III Touring Riese & Muller in 2021 but came with no factory light, but the shop added some position lights

On the Birdy III Touring from Riese & Müller, the lights are optional.

With this option, the Birdy has a Shutter Precision dynamo hub (a specific one for the Birdy disc, SON had also a specific SON XS Birdy disc hub dynamo but I think its discontinued?), a Supernova E3 Pure 3 front light and a Supernova E3 tail 2 light.

Hello,

I got a second-hand gen3 City from 2021 in pretty good condition, and have a few questions:

1. To replace the old solution Birdy used, what chain tensioner should I get? Are there cheaper alternatives to Pacific Cycles' that are just as good?

2. Since I'll be using that bike mostly for touring, I'd like to replace the Nexus 8 with a Sturmey-Archer CS-RK3 hybrid hub like Pacific Cycles did after SRAM stopped making its DualDrive… but couldn't find pictures on the Net on how/where they stuck the housing stop. Does someone know?

3. The SP SD-8 dynamo shows a lot of friction — the wheels stop spinning after just a few seconds. Since I very rarely ride at night anyway, I'm thinking of ditching it and installing a plain hub. Is it possible?

4. Since I use an Ortlieb Rack-Pack bag instead of panniers, I'd like to replace the Expedition rack with a low-rise rack like Birdy used to sell. And still be able to easily roll the bike folded. What are the options today?

5. For some reason, the two wires that power the rear light are unstuck. What's the clean way to fix it?

6. I weigh about 77kg/170lbs: Should I replace the front (it's pretty soft), and rear (pretty hard) suspensions?

Thank you.

https://cimg9.ibsrv.net/gimg/bikefor...a60314da28.jpg
https://cimg1.ibsrv.net/gimg/bikefor...618dd3100a.png
https://cimg6.ibsrv.net/gimg/bikefor...b07b08c3de.png
https://cimg7.ibsrv.net/gimg/bikefor...d446f9c6f0.jpg
https://cimg8.ibsrv.net/gimg/bikefor...a242dd5d13.jpg

For the chain tensionner, the original one around the chainring is excellent, it works really well with as consequence that there is no market for a third party solution. Since you are in Paris, no need to buy it online from Pacific Cycles, any Riese & Müller reseller can order it and provide you that tensionner. And I think that Les Vélos Parisiens is still selling the Birdy, they should be able to provide you all needed spare parts.

The Birdy disc front hub is not a standard 100mm OLD disc front hub, the position of the disc is closer to the center of the hub than on a standard front disc hub. The Shutter Precision hub dynamo is a special type made for the Birdy with the mounting for the disc on the right position for the Birdy disc. There are third party Birdy disc front hub available for instance from Hubsmith or from Ridea. But again, you can ask a Riese & Müller to order such a front hub which is mounted on the Birdy without hub dynamo.

For the rear rack, the folding rear rack is excellent, it doesn't modify the folded size. There are third party fixed rear rack but they increase the folded size.

The red rear suspension block is OK for your weight, you do not need the green harder or yellow softer block.

For the front suspension, there are two hardness of springs, I recommend the hard one with 8.5 coils (the softer one has 10.5 coil). By default, Riese & Müller mount the harder 8.5 coil spring and Pacific Cycles the softer 10.5 coil. There are also several hardness for the rubber damper inside of the front spring but they have little influence on the front suspension, its the spring hardness which is important. But yours seems pretty old and should be replaced.

I have no idea how to mount the SA 3s IGH as mounted on the Pacific Cycles Birdy Touring. In case of change of the rear hub, you should know that Riese & Müller adapt the crank chainline to the rear hub chainline by adding spacer on the bottom bracket, the Birdy Rohloff for instance has different spacers and a different chanline value than the R&M Birdy Touring for 10s cassette.
For me, the best transmission for the Birdy, the one that provide the best efficiency and ride pleasure is the cassette+derailleur type as mounted on the R&M Birdy Touring. I would never mount such an heavy and inefficient SA 3s IGH on a Birdy (nor would I buy a Birdy City with 8s Shimano IGH).

Thanks for the input. I'll see if R&M stores can order the chain tensioner + hub+ front suspension kit.

I still prefer a low-rise rear rack. I'll see if I can find one like the one used by Jon Worth that doesn't increase the folded size, and ideally let me roll the bike.

As an alternative to the S-A hybrid hub, what parts should I get to mount a double chainring (clamp, derailleur, shifter, crankset, cassette, derailleur)?

https://cimg1.ibsrv.net/gimg/bikefor...d32506983f.png

What's the rubber damper for in the front suspension? Do I need one?

Since PC's chain tensioner is $115… what about this one from Alltoo that sells for €13 on AliE? Does it work without the chain tensioner in the back (since this is the whole point)?

https://cimg2.ibsrv.net/gimg/bikefor...b1e32d0a85.png

The difference is that the new tensionner of the Birdy 3 is not rigid as this one (and several others), its a spring loaded deformable parallelogram. Due to this concept, it works without any extension on the derailleur cage.

This new tensionner is not specific to Pacific Cycles, its also a R&M development, the Birdy 3 touring (10s derailleur) and Birdy 3 Rohloff of R&M are equipped with this tensionner, its only the Birdy 3 City that doesn't have it.

This is the tensionner sold by a Dutch R&M reseller (Kemper Fietsen).
And this is the damper of the front fork which seems cracked on your Birdy.

Unfortunately, they ship only to The Netherlands and Belgium

So it's a better alternative to eg. Ridea's or Litepro's, which require pulling the chain before folding the bike?

https://i.ebayimg.com/images/g/zKkAA...e/s-l1600.webp

With the Birdy 3 tensionner, there is no need to do anything like pulling the chain, just folding the rear swing arm, same as when folding the rear triangle of a Brompton with the Brompton chain tensionner.

The only difference with a Birdy with a cassette+derailleur is that the chain must be placed on the smallest cog to be able to fully fold the rear swing arm but this has nothing to do with the chain tensionner.

It seems that you are in Paris, if its the case why not test the folding of a Birdy Touring or Rohloff with this tensionner at Les Vélos Parisiens and decide if its worth its price?

It saves me the trip. Thank you.

On another folder, I just test-rode the CS-RK3 that replaced a regular cassette + double crankset: It doesn't feel any different in terms of performance. I'll report back after a multi-day outing.

The cassette mounted on the R&M Birdy Touring is a 9-32t. This range is enough for most uses without the need of a double crankset and weight much less than a CS-RK3.

On my Birdy, I replaced the Sunrace rear hub and cassette by a Tune hub+Ethirteen 9-34 cassette+Shimano RD-R8000GS with a little more range and less weight.